Attached you'll find a log created using the tips from the Wiki (ekiga -d 4
2>output.txt). After I ran Ekiga, I tried to contact "echo service" with
no success (but there were no problems, when I tried it yesterday with

This is a known and unfortunate ekiga problem: your UDP packets are
greater than 1500 bytes, so they do not reach the destination. Remove 5
or more unused video and audio codecs and try again. grep large
output.txt should not show anything.

Linphone). Another strange thing is, that although I'm able to point the
wanted audio devices in "preferences", the audio-related menu points totally
"grayed out" in menus (perhaps it'll become active only on connection?).

I do not see what you are taking about, could you be precise?
Have you executed make install? Look: